Products > Test Equipment
HP8595E spectrum Analyzer: readings at -40dB and CAL SIGNAL NOT FOUND
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DavidAlfa:
Modern DMMs will source pretty low currents, last one I measured did 2mA, was a supercheap meter.
That would put 100mV, 200uW (-7dBm) on the 50Ohm RF input.
I guess good DMMs will provide way lower current.
Would that small DC signal be able to cause any real damage?
rf-loop:

--- Quote from: DavidAlfa on December 12, 2023, 03:16:59 pm ---I said doing so between the input and output of the attenuator, which means both sma connectors removed, completely isolated from the analyzer RF input, so no risk of any kind.

--- End quote ---

Yes, of course this is a safe way.

However, I wanted to point this out because I have too often seen when something is done slightly different from the instructions, even if just out of curiosity. If by chance such danger factors were not known.

;) 
MarkL:

--- Quote from: rf-loop on December 12, 2023, 01:04:42 pm ---...
There is also somewhere available full CLIP for these (I have only original paper versions, whole repair service set, long time ago purchased from HP/Agilent)

--- End quote ---
For reference, there is this one that's been copied far and wide, still available from Keysight's server:

  https://www.keysight.com/us/en/assets/9018-05708/user-manuals/9018-05708.pdf

CLIP part number 5963-2951.

It's titled "8590A Component Level Information Packet" (CLIP) on the opening page, but it's actually a CLIP for 859xE/L/C units.  There are nuances for specific E/L/C models and serial number ranges that will appear in other CLIPs, but everything is so similar it doesn't usually matter.

If you ever need to find the exact right CLIP, there is a table on page 521 (Table 12-2) in the Assembly Repair Guide that lists the CLIP part number for specific models and serial number ranges.
auato:
Hello guys, thank you for the valuable advice you've been giving me. I would like to update you on the test you recommended (especially from @MarkL), which involves directly connecting the attenuator output to a second analyzer and injecting a well known amplitude signal from an external generator. I injected 300MHz at +15dB and here are the results below and in the video:

Att 10dB -43dBm
Att 20dB -52dBm
Att 30dB -60dBm
Att 40dB -33dBm
Att 50dB -43dBm
Att 60dB -53dBm
Att 70dB -60dBm



https://youtu.be/8tmC3t8NghE?si=OeWIvvGoLs2DWhDO

With attenuation at 40dB, I get the highest reading (-33dBm from +15dBm).
It seems clear that there is something wrong with the attenuator. If I want to exclude the rigid connection and the N connector upstream of the attenuator I would just have to proceed to disassemble the attenuator and try to get my hands on it  :-\
rf-loop:

--- Quote from: auato on December 16, 2023, 09:19:58 pm ---Hello guys, thank you for the valuable advice you've been giving me. I would like to update you on the test you recommended (especially from @MarkL), which involves directly connecting the attenuator output to a second analyzer and injecting a well known amplitude signal from an external generator. I injected 300MHz at +15dB and here are the results below and in the video:

Att 10dB -43dBm
Att 20dB -52dBm
Att 30dB -60dBm
Att 40dB -33dBm
Att 50dB -43dBm
Att 60dB -53dBm
Att 70dB -60dBm



https://youtu.be/8tmC3t8NghE?si=OeWIvvGoLs2DWhDO

With attenuation at 40dB, I get the highest reading (-33dBm from +15dBm).
It seems clear that there is something wrong with the attenuator. If I want to exclude the rigid connection and the N connector upstream of the attenuator I would just have to proceed to disassemble the attenuator and try to get my hands on it  :-\

--- End quote ---

Once the attenuator is removed and it is on your desk.

Carefully remove the second end piece (4 screws)
Don't open anything else yet!

There is a metal mesh between the end piece and the frame. Note its positioning. also be careful that no dirty / dust of any kind gets into the exposed attenuator cavity.

After the end piece is removed, pull out the aluminum protective case. You can then fasten the end piece back in place (even if only with a couple of screws, just a light finger-tightness) It is also good to be in its place if repair work go forward to next step after detect O rings condition. 

Now that the side of the relays is exposed, you can see the nylon pins that control the attenuator contacts. Each one is on the moving plate of the relay and there are black O-rings. Check carefully whether all O-rings are completely intact. At this stage, you can also move each relay by hand and it will stay in the position you press because of the magnet. In this case, you can see better that all the O rings are in order and that the pins move through their full range of motion. Move every relay and check every single O-ring when nylon pin moves when you turn relay in and out.

I have a 50% prediction that the 40dB attenuator bypass position will not work.
Let's hope problem is O-rings... and nothing else.

Do not disassemble or proceed further until this is resolved.
If the O-rings have a typical defect, next you need the right O-rings and information on how to change them so that the risk of further damage is minimal. It requires the skills and precision of a fine mechanic work. Those nylon pins and contact strips inside attenuator cavity and their fastenings in the attenuator cavity are quite easily damaged, as are the attenuator chips. There are also screws that should not be turned if you want the attenuator's properties to remain correct throughout its frequency range (and those things are not compensated by selfcalibration). Before you get there, you have to do a few things in the right order.


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